1. Field of the Invention
The present invention relates to enhanced uplink dedicated channel (Enhanced DCH, hereinafter referred to simply as E-DCH) in WCDMA, especially to the method for supporting pilot boost by transmitting the transport format combination indicator of the E-DCH (E-TFCI) in advance in the E-DCH.
2. Description of the Related Art
FIG. 1 shows the uplink physical channel structure of a user equipment (hereinafter referred to simply as UE) in version R99/Rel-4 in a frequency division duplex (hereinafter referred to simply as FDD) WCDMA system.
101 Dedicated Physical Data Channel (hereinafter referred to simply as DPDCH). In the FDD system, the physical channel includes the dedicated physical data channel and the dedicated physical control channel. The DPDCH is used for transmitting a dedicated channel (hereinafter referred to simply as DCH).
102 Dedicated Physical Control Channel (hereinafter referred to simply as DPCCH). The DPCCH is used for transmitting control information of the physical layer. Gain factors are applied to set the power ratio for the corresponding DPDCH and DPCCH respectively. The DPCCH is composed of pilot, transport format combination indicator (hereinafter referred to simply as TFCI), feedback information (hereinafter referred to simply as FBI) and transmit power control commands (hereinafter referred to simply as TPC).
102A Pilot which is used for channel estimation and power control. In the wireless communication system, it is difficult to recover the transmitted signal by directly processing the received signal since the wireless channel has made some modification to the phase of the transmitted signal. To solve this problem, the transmitter should transmit some known training sequences. Therefore, the receiver can recover the phase of the transmit signal by obtaining the information on the channel from the received training sequence so as to improve the correctness of signal receiving. This process is called channel estimation. The pilot is a kind of training sequence for channel estimation. In addition, because the pilot is a known sequence and the measure of Signal-to-Interference Ratio (hereinafter referred to simply as SIR) is easily conducted for it, it is also often used for power control.
102B TFCI which is the concept of TFCI is specially described in the following section.
102C FBI which is used for transmitting the feedback information from the UE to the network in the techniques such as closed-loop transmit diversity and site selection diversity transmit power control.
102D TPC which is the uplink transmitted TPC of the UE are used for power control on the downlink transmitted signal of Node B.
Now, the concept of the TFCI will be explained. In the WCDMA system, the transport channels are services that the physical layer provides to the higher layers. The DCH mentioned above is one of the transport channels. Within one transmission time interval (hereinafter referred to simply as TTI), the physical layer exchanges transport blocks which is from zero to several with the media access control layer (hereinafter referred to simply as MAC) in one transport channel. At present, the TTI of the DCH in the FDD can be 10 ms, 20 ms, 40 ms or 80 ms. The number of bits in each transport block is called transport block size (hereinafter referred to simply as TBS). The set of transport blocks within one TTI of a transport channel is called the transport block set. The number of bits in one transport block set is called transport block set size (hereinafter referred to simply as TBSS). One transport channel or more can be multiplexed to one code composite transport channel (hereinafter referred to simply as CCTrCH) simultaneously and then mapped to the physical layer. The TBS reflects the data rate of the transport channel, while the TBSS reflects the total data rate of CCTrCH. For the transport channel, the format used for data exchanging between the physical layer and the MAC layer within one TTI is defined as the transport format (hereinafter referred to simply as TF). The TF mainly includes the TBS and the TBSS. The set of transport formats corresponding to each transport channel is called transport format set. The number of each TF in the transport format set is called the transport format indicator (hereinafter referred to simply as TFI). In the CCTrCH, one combination of the TF of one transport channel is called transport format combination (hereinafter referred to simply as TFC). The TFCI is used for notifying the receiver of the TFC mapped to the current CCTrCH so as to receive the DPDCH correctly. With the received TFCI, the TFI of each transport channel in the CCTrCH can be obtained so that the receiving end can decode the information included in each transport channel. In existing systems, the TFCI and the DPDCH corresponding to it are transmitted simultaneously.
FIG. 2 shows the process of generating, transmitting and receiving the TFCI in the WCDMA system. In the transmitter of the UE, two dedicated channels 201 and 205 are multiplexed to one CCTrCH. The Dedicated channel 201 corresponding to the TFI 202 includes two transport blocks, i.e., block 203 and 204. Similarly, the dedicated channel 205 corresponding to the TFI 206 includes two transport blocks, i.e., block 207 and 208. The TFI 202 and the TFI 206 are combined and indicated with the TFCI 209 by the physical layer of the UE. Then, the TFCI 209 is multiplexed into the DPCCH 210 after it is encoded by the physical layer of the UE and transport block 203, 204, 207 and 208 are transmitted through the DPDCH 212 after they are encoded and multiplexed (this process is implemented by the module 211). The DPCCH 210 and DPDCH 212 are transmitted via the wireless channel to reach the base station (hereinafter referred to simply as Node B). The Node B obtains the TFCI 214 from the received DPCCH 213, and the TFI 217 of dedicated channel 201 and the TFI 220 of dedicated channel 205 are obtained after the TFCI 214 is decoded. The Node B obtains the transport block 219 and 218 after decoding and demultiplexing the module 216 according to the TFI 217, and the transport block 219 and 218 correspond to the transmitted block 203 and 204 respectively. Similarly, the Node B obtains transport block 222 and 221 after decoding and demultiplexing the module 216 according to the TFI 220, and the transport block 222 and 221 correspond to the transmitted block 207 and 208 respectively.
The E-DCH is a research issue on enhancing the existing uplink dedicated channels under the standardization by 3rd Generation Partnership Project (hereinafter referred to simply as 3GPP). The object of the research is to improve the uplink system performance for the FDD system by studying on techniques of adaptive modulation & coding, hybrid automatic repeat request and Node B controlled scheduling. The concepts of E-DCH, E-DPDCH, E-DPCCH and E-TFCI have been introduced in the research of E-DCH. The E-DCH per se is a new kind of dedicated transport channel or an improved to the existing DCH. It should be noted that the E-DCH represents following two aspects in the present application: the research project and the research object in the project. Similar to the relationship between the E-DCH and the DCH, the E-DPDCH is a new kind of dedicated physical data channel or an improved to the existing DPDCH. Likewise, the E-DPCCH is the new kind of dedicated physical control channel associating to the E-DPDCH or an improved to the existing DPCCH. Several DCHs and E-DCHs can exist in the uplink transport channel of the UE. Following two multiplexing methods can be applied in the E-DCH and the existing DCH: the time division multiplexing (hereinafter referred to simply as TDM) and the code division multiplexing (hereinafter referred to simply as CDM). Here, the former means that the E-DCH and the DCH are multiplexed to the same code channel, while the latter to different ones, i.e., different code channels are adopted in the E-DPDCH and the DPDCH. Corresponding to the E-DCH, the E-TFCI is adopted to indicate the transport format combination of the E-DCH. After the concept of the E-TFCI has been introduced in the present application and for the convenience of distinguishing, the TFCI corresponding to the DCH is called D-TFCI, which indicates the transport format combination of the DCH. The E-TFCI can be transmitted via the existing DPCCH, i.e., the E-TFCI and the D-TFCI can be multiplexed to TFCI 102B of DPCCH with the method of coding. Also, the E-TFCI can be transmitted via the physical channel (e.g., E-DPCCH) other than the DPCCH.
In the CDMA system, the power control is the very important approach in solving the problem of near-far effect and improving the system capacity. The power control includes two levels of inner loop power control and the outer loop power control. The outer loop power control sets the target for the inner loop power control according to the requirements of the QoS. And the inner loop power control adjusts the transmitting power according to the target preset by the outer loop power control, that is, adjusting the received SIR within the permitted range of the target of the inner loop power control (hereinafter referred to simply as SIRtarget). In the FDD system, the inner loop power control operates once in every time slot (Slot for short). The uplink inner loop power control refers to the one that the Node B controls uplink transmitting power of the UE. And the downlink inner loop power control refers to the one that UE controls downlink transmitting power of the Node B.
FIG. 3 illustrates the process that the uplink inner loop power control operates in the existing WCDMA system. Data 301 transmitted from the UE reaches the base station after it is adjusted by the transmitting power control module 302 and passes through the radio channel. Denote the SIR that the Node B has measured for the uplink DPCCH by SIRest. The SIRest is obtained mainly by measuring the pilot, or it can be obtained by the measured data or other techniques. In the comparing and judging module 304, the Node B compares the SIRest with the SIRtarget and if the SIRest is less than the SIRtarget, the Node B sends the “TPC UP” command to the UE to increase the transmitting power; otherwise, it sends the “TPC DOWN” command to the UE to decrease the transmitting power. In the existing system, the SIRtarget per se is adjusted by the outer loop power control but this adjustment has nothing to do with the data rate. The TPC commands 305 sent from the Node B are transmitted to the UE via the radio channel 306. Having received the downlink TPC command, the UE adjusts the transmitting power for the uplink DPCCH, DPDCH and E-DPDCH (only in the E-DCH) according to the requirement of the received TPC command in the transmitting power control module 302. The adjustment amplitude called the power control step size that UE operates to the transmitting power is specified by the network. In current WCDMA standard, the power control step size can be 1 dB, 2 dB or 3 dB. The power adjustment of the DPCCH can be calculated by equation (1) below:ΔDPCCH=ΔTPC×TPC—cmd  (1)
Where: ΔTPC stands for the power control step size; TPC_cmd is determined by the downlink TPC sent from the Node B. When Node B sends the TPC UP via the downlink, TPC_cmd=+1; otherwise, TPC_cmd=−1. For instance, when the power control step is 2 dB and the Node B sends TPC UP via the downlink, the UE boost the transmission power by 2 dB for the DPCCH.
The UE adjusts the transmitting power for other physical channels other than the DPCCH according to the corresponding gain factors. Every physical channel has a gain factor corresponding to a TFC. FIG. 9 shows the structure of a kind of physical channel of E-DCH. All four physical channels like 901, 902, 903 and 904 corresponding to DPDCH, E-DPCCH, E-DPDCH and DPCCH respectively are shown in FIG. 9. In the uplink of the FDD system, every physical channel requires the process of spreading, then multiplies by the gain factor. cd, cT, ceu/d and cc are the channel codes for the DPDCH, E-DPCCH, E-DPDCH and DPCCH respectively. And the corresponding gain factors are βd, βT, βeu/d and βc respectively. The DPDCH's spreading module and product of gain factor module are 905 and 909 respectively. Similarly, the spreading module and the product of gain factor module of the E-DPCCH are 906 and 910 respectively, spreading module and product of gain factor module of the E-DPDCH are 907 and 911 respectively, and the spreading module and product of gain factor module of the DPCCH are 908 and 912 respectively. The data of the DPDCH multiplied by the gain factor and that of E-DPCCH multiplied by the gain factor are added in the adder 913 to yield the data of branch I. The data of the E-DPDCH multiplied by the gain factor and that of the DPCCH multiplied by the gain factor are added in the adder 914 and multiply by j in procedure 915 to yield the data of branch Q. Finally, data of branch I and Q pass through the adder 916 to yield the data of base band signal. Above is the explanation to the structure of a kind of physical channel of E-DCH. It should be noted that the transmitting power of any other physical channel other than the DPCCH can be determined by the corresponding gain factor, i.e., the transmitting power of any other physical other than the DPCCH is determined when that of the DPCCH has been adjusted according to the downlink TPC commands.
In the wireless communication system, reducing the SNR (signal-to-noise ratio) of the receiver will improve the capacity of the entire system on condition that certain QoS is satisfied. In the research of E-DCH, it is found that: proper boosting of the pilot SIR for the high rate data can improve the performance of channel estimation, therefore the SNR of all signals of the UE for the Node B has been greatly reduced so that the system capacity has been improved. This idea is called pilot boost. However, in the existing system, the pilot SIR has nothing to do with the application data rate but is under the control of the outer loop power control. The inner loop power control aims at adjusting the pilot SIR to approach the target preset by the outer loop power control. If the pilot SIR is boosted, the Node B will make a wrong assumption that channels have been improved. Consequently, the pilot SIR will be reduced to its original level through the power control. So, the object of improving the pilot SIR for high data rate system can not be reached simply through increasing the pilot SIR with no other associated techniques.